This is not possible out of the box.
But if you plan to implement something like this, then don't do it at the category level. Better do it on the attribute set level, because a product can be in one or more categories (or none).
Here is an idea on how you can do it. (sorry but no code).
You can add a new column on the table
attribute_set_id, then add a new field in the form that adds/edits the rating option with all possible attribute sets (and an additional option with the value 0 for all attribute sets).
Then rewrite the method
Mage_Review_Block_Form::getRatings and include an other filter based on the current product attribute set id.
And here is where my ideas stop. One last thing... you have to go through the full process of posting some ratings and make sure that all the code involved takes into consideration only the ratings available for the specific attribute set of the product.